Case Study

Machine Vision Sensor Provides Quality Control for Cap-On Detector

21st Century Manufacturing, Inc. (21M; Danbury, CT) manufactures material handling equipment ranging from custom-designed, one-of-a-kind packaging systems to standard conveying systems. 21st Century's customers demand equipment that is highly flexible, mobile and cost-effective so it can accommodate a variety of material handling configurations and the frequent changes that are made to these configurations. "21M," as the company is called, is always on the lookout for ways to offer these advantages to their customers.

Engineers from 21st Century recently designed a system called the "Cap-Sure Detector" for a pharmaceutical manufacturer. This modular system is placed over a conveyor and is used for in-line inspection to determine whether a bottle cap is on a bottle and, if so, whether the cap is on straight. This type of inspection can be solved easily by a photoelectric sensorunless the system will be moved from location to location and the size and shape of the products being detected will change frequently. In this case, the amount of time required to move and re-adjust sensors to accommodate product changeover is prohibitive in terms of sacrificed reliability and lost production time.

"I needed a solution that is small, can be quickly and easily mounted and re-adjusted to allow rapid changeover," says Zsolt Toth, Director of Engineering at 21st Century. "I didn't know whether something like that existed for a price that our customers were willing to assume in the cost of the machine."

Having purchased Omron programmable logic controllers, operator interfaces, and sensors in the past, Toth contacted Omron distributor Control Solutions New England (Bloomfield, CT) to see if Omron offered such a product. The company's recently introduced F-30 machine vision sensor turned out to be the perfect solution for this application.

Incorporating all of the elements of a machine vision system (camera lens, lighting, and processor) into one compact 3" x 3" x 6" assembly that can be set up easily in a matter of minutes with no software programming, the F-30 was designed as a low-cost, easy-to-use presence/absence and parts orientation detection solution. For 21M's application, the F-30 was installed on an adjustable screw on the side of the Cap-Sure Detector (see photograph). The F-30 vision sensor can be moved up or down in a matter of seconds to look at the tops of bottles coming down the line, whatever size the bottles might be. The unit is locked in place when it reaches the proper height, inspection parameters are set up in minutes using the F-30's five-key console (four up and down arrows, one "enter" key), and the system is ready to run.

How does the F-30 vision sensor ensure that caps are present on bottles and that they are positioned properly? Following simple, step-by-step onscreen instructions, the user enters five different parameters into the system: inspection area, contrast between background and object being detected, whether the F-30 should count black or white pixels, tolerance, and the number of pixels to be used as the "gold standard" during inspection. The F30 has three outputs: OK, LOW, and HIGH. If a product's pixel count falls within the parameters entered into the system, the OK output goes on and the product continues down the conveyor. If no cap is present, if the cap is skewed or if it is not twisted on all the way, the pixel count will be lower or higher than that established for a good product. When the LOW or HIGH output is triggered, an air valve diverts the bottle off the production line.

21M engineers also set up an alarm system so that, if a user-determined number of caps per minute are defective, the assembly line is stopped and plant engineers can pinpoint production problems right away. "In addition to being compact, highly flexible and easy to use, the F-30 gives our customers additional production monitoring capabilities we hadn't anticipated," says Toth.

The customer for whom the first Cap-Sure Detector was built, a generic solid-dosage pharmaceutical manufacturer, has been very happy with the speed, reliability, and flexibility of the new system.

"The system responds very quickly, ejecting a bottle with no cap or with a skewed cap offline in a fraction of a second," says Simon Yang, Project Engineer. With production requirements of up to 80-90 bottles per minute, and with product changeover "at least two times per day," it was crucial that the inspection process did not affect manufacturing speed. After several months of qualifying the machine, engineers are satisfied that the F30 machine vision sensor will do the job quickly and reliably.

The price tag for the new vision system, according to 21M, was far below the cost for traditional machine vision systems that require programming, user training, and knowledge of vision and lighting. And, while the up-front cost is more than users would pay for a photoelectric sensor, the savings in time spent re-adjusting sensorsand production line downtime while these adjustments are being donemore than pays for itself.

"Clearly, the capabilities of the vision sensor are such that we can use it in a variety of ways, both for different applications with this system (such as label detection) and on other types of systems we build in the future. We are very excited about the many highly flexible, cost-effective quality control options the F-30 offers to us and our customers," concludes Toth.